A color filter is used in a color face plate for Braun tube display, a photoelectric conversion element plate for copying use, a single-tube color television camera filter, a flat panel display using liquid crystals, a color solid image pick-up element, etc.
A common color filter is generally constituted of regularly arranged red, green and blue colors (i.e., three primary colors), but it may have four or more different hues, if needed. For instance, color filters for use in an image pickup tube and a liquid crystal display apparatus require a black pattern (black matrix) for various purposes.
As for the way of arranging red, green and blue colors, mosaic, stripe and delta arrangements are exemplified as examples thereof. How to arrange those colors can be chosen so that the color filter meets requirements for the intended use.
Hitherto known methods for producing color filters include an evaporation method, a dyeing method, a printing method, a pigment dispersion method, an electrodeposition method, a resist electrodeposition transfer method, and so on. However, color filters obtained by these conventional methods have several disadvantages, such as involvement of complicated steps, liability to pinholes or scratches, poor yield, insufficient precision, etc.
In order to overcome these disadvantages, production of color filters using a silver halide photosensitive material of coupler-in-developer type (see JP-A-55-6342, the term "JP-A" as used herein means an "unexamined published Japanese patent application") or coupler-in-emulsion type (see JP-A-62-148952 and JP-A-62-71950) has been studied. However, the coupler-in-developer type development involves at least three times of color development and is not deemed to be simple and easy to carry out. In the coupler-in-emulsion type, on the other hand, the color filter obtained has a large thickness, and tends to suffer peeling during rubbing treatment in the production of an LCD panel or cutting of lines. In particular, it has been difficult to obtain a sharp pattern from the coupler-in-emulsion type color photosensitive material because the material have many photosensitive layer and therefore have a large thickness.
In order to solve those problems, it could be thought that the coating amount of a binder be reduced. However, it turned out that the reduction of a binder coating amount resulted in a relative increase of the proportion of low melting organic compounds in the coated layers to make the generated dyes diffuse easily under a high temperature, thereby causing a problem of providing a blurred pixel pattern.
When used, for example, in color LCD, a color filter is unavoidably exposed to high temperatures above 150.degree. C. in post-treatments, such as coating with a protective layer, vacuum deposition of a transparent electrode, and formation of an orientation film. Accordingly, the dyes used in a color filter are required to be fast and not to be diffused in such high temperatures.
The dyes are also required to have high light fastness because color filters are to be exposed to back light for extended time periods.